Gravitational lensing has been confirmed several times by observation of a stars during full solar eclipses. The first confirmation came in 1970.

Hawking Radiation theoretically occurs regardless of whether the black hole is "feeding" or not.

Hawking radiation for such large BH must be colder than background radiation. Thus, this BH will suck on the background radiation more, than emit.

@AlexG

I don't think that temperatures have anything to do with it. Hawking Radiation is the result of virtual particles popping into existence (also theorized as vacuum energy or Dark Eneregy) near the event horizon. When the particle pairs (made up of a particle and its anti-particle) don't anhilate each other, one particle falls into the black hole while its partner escapes as radiation.

David9000

... hawking radiation can be observed. That would be a significant step in confirming black hole and relativity theories.

Hawking radiation is just an ego generated equation filler 'balancer' to allow the CERN experiment to proceed with out delay, and a 'tending to infinity' limit risk...

It is based on the postulates of one who fillip-flops in his thinking, can't get up from his seat on his own steam, and has no hostage to offer, to a black hole 'error', in the next generation - NO SKIN IN THE GAME!

Hawking radiation, if it does exist would be the major surprise in physics...I would not count on it. More likely a black hole explodes through a 'white-hole' into the creation field...NOT as radiation but as matter, as in a constant spew of atoms appearing as if out of nothing - proving the Creation Field hypothesis.

hamz~ its rather amusing, if not also sad, that you discredit hawking radiation as filler, only to bring up your own filler explanation of white holes. something that only exists as a mathematical construct. and to criticize hawking as being a flip flopper makes me doubt you're ability to understand on of the most basic aspect of the scientific method... we follow evidence, not emotion.

God flushes galaxies down the black hole toilets...

@Scott M - Yes, graviatinal lensing has been observed using very large scales such as galactic clusters. But observing gravitational lensing from a very small object such as a black hole could be used to confirm the physical characteristics of a black hole.

WRT hawking radiation, when a black hole is 'feeding', the resulting radiation from matter compression would overwhelm the ability to detect hawking radiation. By observing hawking radiation from a 'quiet' black hole, they could confirm Hawking's theories about loss of information (or information retention) between the universe and black holes which would go a long way to confirming black hole theories in general.

@Scott,

Hawking radiation, just like a black body emission, is characterised by effective temperature, which is the higher the smaller BH is. Peak wavelength of its power distribution would be proportional to the BH size.

@ David9000

The physical characteristics that could be confirmed about a black hole by obseration of gravitational lensing, would simply be the same characteristics that are already confirmable by the orbits and speeds of the bodies being affected by the gravity of the black hole. Observations of gravitational lensing aren't needed to confirm what we've already confirmed through visual observation that matches what Newtons Laws and Einstein's equations say we should observe.

In short, the observance of gravitational lensing caused by the graivity of a black hole wouldn't really do anything to advance our knowledge of physics, which is what I suspect the original comment was implying it would do.

As for Hawking Radiation, you are correct that it would be very difficult to detect it while the black hole is feeding, but your connecting Hawking Radiation to the Information Paradox is unfounded as the two are separate concepts. What it would do is allow (over millions of years) Hawking's theory that black holes evaporate to be tested.

@AlexG

I'm still not sure why you are presenting information about temperatures, when Hawking Radiation is caused by virtual particle pairs spontaneously appearing very close to the event horizon of a black hole and one of them is pulled into the black hole, while the other is ejected as radiation.

If the black hole is feeding, the inward mass would obscure the detection of this miniscule outward "leakage". If the black hole is not feeding, the radiation is more detectable. But, and as my original reply was intended to convey, this radiation is emitted all the time, it's just harder to detect when the black hole is in an active state.

I cannot wait to see the pics!

Then maybe we'll "know" which is right, what I was first taught @ Eberly (PSU) or what is now being taught. Learning and re-learning the theories/math was fun for sure! Let's hope that there isn't something else to "learn"! ;-)

As for HR, my hunch is that it'll be eventually forgotten. That it is a mathematical "possibility" akin to the mathematical possibility of Japanese Navy beating the US Navy in WWII, possible but highly improbable. The effective evolution from the BH (or dark star) to non BH will be an actual event versus the theoretical possibility of HR. In the end I completely expect science to realize that our theories vastly overshot reality, mostly due to our still limited observational capabilities.

@Scott M - We're going to have differing opnions on how observed gravitational lensing around a BH will advance theoretical science. But I do contend that Hawking Radiation was Hawking's answer to the Information Paradox since it allows for information to be returned to the universe through BH 'evaporation' rather than being permanently lost in the BH.

@David

Hawking believes that the "Information Paradox" is solved via Hawking Radiation, but he doesn't have much of a following in the scientific community for the connection between the two.

If you agree with Hawking then you are essentially agreeing that information that was "inside" that black hole is somehow returned to our universe when/as the black hole evaporates. But this means that matter from "within" the black hole is somehow moved from inside to outside and that is not what Hawking Radiation is or comes from. Hawking Radiation eminates from just outside the event horizon of the black hole, not from within it.

Leonard Susskind had a 20 year long bet with Hawking that information was not lost in the first place (Hawking believed that information, beyond some basic atomic characteristics of the particles going into the black hole, was lost). Hawking eventually conceded that bet, but although he now believes that informaiton is not lost, his view on why is not considered to be in the main stream.

There seems to be more of a consensus (and some mathematical models) that information is imprinted on the event horizon surface of the black hole and therefore not lost "inside" the black hole.

If you subscribe to this theory, which I do, then there is no relationship between Hawking Radiation and The Information Paradox.

@Scott,

From an article on HR theory:

"For astronomical black holes, the evaporation time is prodigiously long - about 10⁶¹ times the age of the Universe for a 30 solar mass black hole."

HR average power corresponds to one photone with wavelength equal to the EH diameter emitted once per time it takes light to cross EH diameter.

@AlexG

What point are you trying to make?

@Scott M - Seems we've ended up in the same place as the physics community... several possibilities but nothing definitive. Hence the need for more scientific observation. Whatever the case, I'm really looking forward to seeing if they can pull off the collective effort and what their observations reveal.

P.S. sorry for the atrocious spelling earlier... bad case of keyboard dyslexia today :)

Scott,

The point is that the black holes won't evaporate. Even if a black hole of typical size doesn't have any other matter falling on it, it still feeds on the cosmic background radiation. To be HR-positive, it needs to be pretty small, as small as to have its HR effective temperature higher than the background radiation temerature (about 4 K).

I'm sure glad we had some random Internet halfwit to straighten out all those PhD astrophysicists.

@Alex

Well, I think that Hawking and the physics community at large would be interested in your paper on this, because this is not the view that is generally accepted.

You keep talking about temperature differences, but I don't think you really understand what Hawking Radiation actually is and that virtual particle pairs are real.

James-4436154

hamz~ its rather amusing, if not also sad, that you discredit hawking radiation as filler, only to bring up your own filler explanation of white holes

... we follow evidence, not emotion.

Exactly!

"Hawking showed that quantum effects allow black holes to emit exact black body radiation, which is the average thermal radiation emitted by an idealized thermal source known as a black body. The electromagnetic radiation is as if it were emitted by a black body with a temperature that is inversely proportional to the black hole's mass."

"A black hole of one solar mass has a temperature of only 60 nanokelvins; in fact, such a black hole would absorb far more cosmic microwave background radiation than it emits. A black hole of 4.5 × 10^22 kg (about the mass of the Moon) would be in equilibrium at 2.7 kelvin, absorbing as much radiation as it emits. Yet smaller primordial black holes would emit more than they absorb, and thereby lose mass."

We will know a lot more about black holes in the next three years. This is a great collaboration! I look forward to the information that the even horizon telescope collaboration will bring.

@AlecG

"Black-Body" radiation and "Hawking Radiation" are two different concepts that are loosely tied together in the case of a black hole.

Hawking Radiation is caused when virtual particle pairs sponteaneously appear just outside a black hole's event horizon. Usually these pairs appear as a paricle and its anti-particle anhiliating each other immediately, but sometimes one particle can be pulled into the black hole, while the other escapes. Technically, the black hole is not "emitting" anything (as black holes cannot do this. The escaping particle is percieved as radiation.

@Scott,

Total mass/energy lost by the black hole via HR (as Hawking stipulates) obeys the same formula as Planck radiation of black body, and is described by its eqilvalent temperature. The point I was trying to get through to you was that only very small (less than 4.5 × 10^22 kg) black holes emit more mass/energy than they absorb from the background radiation. This means: only those smaller than that will ever evaporate. And this is what every writeup on HR will tell you (and will also mention the equivalent temperature, etc); this is not my speculation.

And this is what every writeup on HR will tell you (and will also mention the equivalent temperature, etc); this is not my speculation.

And yet, everything I've ever seen and read about Hawking Radiation indicates that all black holes, regardless of size, will evaporate after they stop feeding. I have not seen or heard about the background cosmic radiation being enough to counter this effect and this is why I continue to debate you on this.

Only if the universe were infinitely old. Being finitely old, we haven't been sucked into one yet, but may eventually cross one's path, I dunno, billions of years from now.

Besides, gravity only operates at the speed of light and its force of attraction gets weaker the further away you get. So if you're wondering why the black hole at the center of the Milky Way hasn't pulled us in yet, its force of attraction is pretty weak at this distance, so we're able to keep from falling in by going in a circle, or "orbit," around it. Same reason space ships don't fall to earth in real life.

Very appropriate username there, by the way.

Maybe we are. The sky is dark at night. Why?

No. We're too far away. Someday though, if the Earth still exists, it could get sucked up by one (although if the universe is expanding it may not be by the central hole in our galaxy). They're not a theory, just how they work is. You don't have to actually see someone to know they're there - just their shadow.

I'm not a scientist but I'd like to play one on T.V.

Gravitationally speaking, black holes are no different than their predecessors, a massive (or in this case an apparent massive collection of) stars minus the little bit of matter expelled during preceding supernova. On this side of the event horizon, even Newton's laws of gravity remain unaffected. Thus, there should be no reason for a black hole to "all of a sudden eat everything up".

Gravity is 4 times weaker for every 2 times the distance away, thus if the sun was all of a sudden a black hole, the planets "wouldn't know it" and would still orbit as normal.

I do not think there is enough matter in the first half of the galaxy to create such an enormous gravitational field strong enough to "ever eat the rest of it up", otherwise, it would seem that we would have ALREADY "merged"!

In reply to my first comment, there should be observations of galaxies further along in their "lives". I like to look at astronomy pictures and do not recall seeing any spiral galaxies with a major proportion of their centers missing...

Also, if the sun was to all of a sudden become one, it would be thousands of times smaller in diameter, and thus have a g-force capable of capturing its own light. But, at ~ 400,000 miles away, at the real surface of the sun, it's gravity is thousands of times weaker, just as the real sun's gravity is.

@Mr. Lobster

Only if the universe were infinitely old.

No, not even in that case. Hawking Radiation is emitted by all black holes and therefore they do not just exist and grow indefinately. Black holes eventually "evaporate" leaving nothing behind.

Black holes will only evaporate, if evaporation loss is faster than accretion gain.

Also, a black hole can't "eat" distant matter, and the distant matter won't suddenly drop into it.

Sun doesn't have enough mass to become a black hole. It will become a white dwarf, IIRC.

What if escape speed from the Universe is speed of light? Meaning it is limited by its own event horizon, and is inside a black hole?

@AlexG-1904848

Black holes will only evaporate, if evaporation loss is faster than accretion gain.

Also, a black hole can't "eat" distant matter, and the distant matter won't suddenly drop into it.

This is exactly why all black holes eventually do evaporate and there aren't 14.7 billion year old black holes that have grown so large that they are gobbling up the entire universe.

Black holes go through "feeding" periods where there is matter falling into their event horizon. During this time, the black hole's mass increases. But, as you point out, the black hole isn't going to suddenly bring matter to it, so when it has "eaten" the matter within its grasp, it goes into an inactive period, where it loses mass due to the emission of Hawking Radiation.

For as large as black holes are, the empty expanses in the universe are much larger. Black holes eventually eat all the matter in their region and then evaporate. This is the ultimate fate of every black hole according to Hawking.

@AlexG-1904848

What if escape speed from the Universe is speed of light? Meaning it is limited by its own event horizon, and is inside a black hole?

Fun idea to think about, but since our observations show that all galaxies are moving away from each other and that our universe is expanding, we couldn't be existing in a black hole because there is no singularity pulling everything together.

@fireofenergy

Also, if the sun was to all of a sudden become one, it would be thousands of times smaller in diameter, and thus have a g-force capable of capturing its own light. But, at ~ 400,000 miles away, at the real surface of the sun, it's gravity is thousands of times weaker, just as the real sun's gravity is.

Not sure where you got 400,000 miles from. Our sun in 93 million miles away.

In reply to my first comment, there should be observations of galaxies further along in their "lives". I like to look at astronomy pictures and do not recall seeing any spiral galaxies with a major proportion of their centers missing...

@Fedup. If the Earth were crushed into a centimeter sized blackhole with the same mass, the Moon would still orbit it, as if nothing had happened. Satellites in Geostationary orbit would not be perturbed. A black hole's gravity is not some mystical tentacle that reaches out and grabs things from a distance, it is simply a deeper gravity well caused by the compression of matter into an ultradense form.

@Scott M, he was refering to the Sun's current photosphere surface, not the distance to Earth.

like every other object with mass, the reach of a black holes gravity isn't infinite, if for instance you replaced the sun with a black hole of equal mass, the orbit of everything in our solar system would stay the same.

Let me say this to that.... We live in a black hole: on the other side. Dark matter can prove this. Just as it bends light it also is lights cop(speed limiter). The big bang happend very fast, faster than the speed of light. How was it faster than light? Because there was no dark matter yet. Or not enough to "matter". Find the key to dark matter and you find the key to everything. But how do you (find) it?

Black holes still sound like a theory to me.

@Scott:

" so when it has "eaten" the matter within its grasp, it goes into an inactive period, where it loses mass due to the emission of Hawking Radiation."

The black holes won't evaporate. Even if a black hole of typical size doesn't have any other matter falling on it, it still feeds on the cosmic background radiation. To be HR-positive, it needs to be pretty small, as small as to have its HR effective temperature higher than the background radiation temperature (about 4 K).

Why are none of you people writing hard Science Fiction?

the least you could do is put all of this speculation into something entertaining for those of us that have to work at mundane jobs that don't involve Life the Universe and Everything.

@AlexG

The black holes won't evaporate. Even if a black hole of typical size doesn't have any other matter falling on it, it still feeds on the cosmic background radiation. To be HR-positive, it needs to be pretty small, as small as to have its HR effective temperature higher than the background radiation temperature (about 4 K).

Where did you get this idea from? It is certainly not something in mainstream physics. Temperatures are not related to the evaporation theory.

James-4436154

like every other object with mass, the reach of a black holes gravity isn't infinite,

You need to brush up on your physics and math, if you ever had any. Gravity, like any other force obeys the inverse square law. Thus, theoretically speaking, what of the black hole, your very own gravity's reach is infinite, and effect infinitely small. LOL

if for instance you replaced the sun with a black hole of equal mass, the orbit of everything in our solar system would stay the same.

Finally you got some thing right!

Exactly, The "virtual" part is where a computer brain puts info fed from different antenna to gether to make one picture. As your brain puts the info from your 2 eyes togethe to form one picture (with some depth to it. Even though each eye only gives a flat (2D) picture, from a single perspective point.

They have been properly accounted for. It's not the magnitude of the mass it's the distribution. If the mass were hiddedn in the center the rotation of the rest of the galaxy would have a radial dependence, but it doesn't, it's almost constant, suggesting much more mass and more uniformly distributed.

Why did you have to sigh? Did it make you feel better or perhaps superior?

There is of course the rebellious theorists proposing a much stronger gravitational force of which we observe only a small portion. The remainder "leaking" into other dimensions which then in some way influences the actions of more distant matter by some process we are as yet unaware of.

An attempt to reconcile the apparent weakness of gravity with a rather large and imposing mass we seem to have a hard time detecting. And there is the hope of the theorists to be able to observe matter or energy residing in our dimensions simply disappearing into thin air. Or as they propose, "leaking" into other dimensions beyond our perception.

Or, another wild goose chase.

You are confusing/combining two separate things and presenting them as if they were one thing.

The "dust and mess" is observable and is just a very dense area of dust, ice and other stellar debris.

The "mysterious dark stuff" that has been theorized to exist in the universe is Dark Matter, which is not mentioned in this article and not relevant to this discussion.

I tell you what, Einstein, why don't you write that up as a research paper for Physical Review. I'm sure they could use a laugh.

No, Ferro, I'm not trying to be smug. I just cannot stomach this nonsense about dark matter Yes, Scott, I know what it supposedly is that I am alluding to when I stated 'mysterious dark stuff'. But what is this dark matter? No one even knows. It doesn't seem to be a part of the Standard Model of subatomic particles. (WIMPS) Could it be an unaccounted number of black holes and brown dwarves? (MACHOS) I don't know.

I'll admit, I am not a trained astrophysicist, but I do not understand why it is necessary to posit the existence of new unknown kinds of stuff to explain the radial motions of these galaxies.

Ferro, your response comes close to addressing what I'm talking about, but I was brief and didn't make myself completely clear. It's not that I think there's additional unaccounted for mass in the form of 'dust and mess' only near the center, I'm questioning whether or not there is more of this dust and mess throughout the entire distribution of these galaxies, out among the arms, perhaps providing enough additional mass to cause enough gravitational attraction to cause the arms to rotate almost as though they were 'solid' (but not really solid, only relatively, in terms of the way they spin), and thereby overcoming the "radial dependance" factor. Does this make sense?

If I'm totally off my rocker in thinking this, please, without sarcasm, fill me in on what I am missing. Otherwise, I'd prefer to think that either our calibrated measurements are wrong or our understanding of gravity needs to be improved before we go surmising the existence of new kinds of 'stuff' that only seems to exist out there and not anywhere near here, so far as we can tell.

Finally, I'm sorry if this is off topic, this question just continues to drive me nuts.

@MikeyMike

If I understand you correctly, you are asking why scientist have come up with the concept of Dark Matter instead of looking at other possiblilities. If that is the case, then answer is that they have looked at all other possibilities that they are aware of and can't account for the reason why the detectable mass in the universe seems to be about 70% short of what it should be.

Dust and ice will reflect light to some degree, so when we examine sample areas in the sky we are able to see (via visible light or via infared or x-ray observations) objects that have mass. But, these objects are simply not plentiful enough (by a wide margin) to have enough gravitiational attraction to hold galaxies together. Therefore, there must be some other kind of matter (matter because gravity acts on objects with mass ie. matter) that is holding the galaxies together.

It wouldn't be black holes because, although we can't see them, we can detect them due to the matter they pull toward them. And, brown dwarfs, although very dim, do emit light and are detectable again because of their very dense gravity well.

The matter that Dark Matter is supposed to represent isn't localized into specific locations (as a black hole or brown dwarf would do). The effect is everywhere and so we're looking for this matter scattered all throughout the universe.

Scott, thanks for taking my question seriously. I am aware of everything which you have stated. I am aware that astromers believe that they have "mapped" certain regions of dark matter in the universe through gravitational lensing effects, so something must be there. I understand all this.

What I don't understand is that if supposedly something like 70% of all the matter in the universe is made up of this special mysterious dark matter, why is there no sign of it more locally, meaning within our own Milky Way galaxy, or within our solar system, and even within this room where I am sitting. If this stuff really exists, then it should exist everywhere.

Conversely, since we detect no evidence of such dark matter here on earth, nor within our solar system (so far as I know), I conjecture that rather than being some special and unique environment which is somehow exempted from the presence of this stuff, we, or our local neighborhood should be taken as the norm, and if it isn't found here, then it won't be found out there either, so there must be something else entirely going on. The only thing I'm left with is miscalibrated measurements.

Now, with all of that said, if the folks at the Large Hadron Collider are able to isolate some new form of matter, not necessarly the Higgs boson, but perhaps some other as yet unexpected particle which has mass and therefore does have a substantial gravitational effect on surrounding matter, but which doesn't absorb and emit light energy in distinct quanta; then we'll talk, but so far as I know the standard model does not even predict the existence of such a thing.

Speaking of the Higgs, we aren't even sure yet if this thing exists. They've gotten close to possibly isolating something which might be a signal of it's presence, but they're not sure. Therefore, we're not yet even sure what mass really is and how gravity really works. Of course, we know that it does work, as Newton apocryphally demonstrated with an apple, but we don't know why. Why do objects with mass attract each other? That would seem to be a natural question for any 5th grade student to ask, and so far as I know, the answer is, "We don't know for sure. We're working on confirming a theory about that, but it hasn't been proven yet." Is there, or is there not a Higgs field? We don't know yet.

Einstein theorized and predicted that it was due to the deformation of space itself. His theory succesfully predicts the way that the path of light is bent in the presence of strong gravitational fields resulting from large masses, an effect which is used to map the supposed existence of dark matter blobs or clouds somewhere's oh way out there, but his theory also predicts the existence of gravity waves, which so far have not been detected. So what gives?

And don't even reply with something like "Massive objects are attracted to each other because mass is attracted to other mass." That's a tautology and doesn't answer anything. The question is WHY and HOW does this work? And until we do know how and why gravity works the way it does, I'll stick with my original postion... I don't see sufficient reason to postulate, surmise or purport the existence of brand new kinds of stuff, the evidence for which is purely circumstantial.

Hey Mikey,

I don't think our instruments are precise enough to detect the gravitational effect locally. Cumulative throughout the galaxy our instruments are precise enough to detect its effect. And they say it should be found most places, including your room.

Now for the hard part. Just because you can't observe it directly, doesn't mean it's not there. Up until just a few years ago, you would never have known that you have billions of neutrinos passing through you at any given second. Even now, to detect them requires a rather incredible piece of kit that sits deep in the ground.

I think you might be getting hung up on the whole 'dark matter' title itself. All it means is that light doesn't interact with it other than by gravity. What that means is that something like neutrinos themselves could be the dark matter we are looking for. We have no idea how much is floating around, as it sits we have a hard time detecting the ones that our Sun is emitting let alone what's in space. We just don't have any way to guess if the density is low, or if we are swimming in an extremely dense sea of this stuff.

"Dark matter" is simply a placer holder name, doesn't mean it's new matter that we don't know about, it's just descriptive of what it is, don't necessarily get wrapped up in the name.

Mitchell

Mitchell - I thought I read somewhere that they had detected a halo of dark matter around the Milky Way.

Mikey - The "stuff" they think makes up dark matter is more exotic than the matter that we see. Things like WIMPS and neutrinos are near the top of there list. The problem with this type of matter is that it does not absorb, reflect or emit light and it can pass through normal matter. We have a neutrino source 93 million miles away, but it takes very sensitive equipment down below the surface of the Earth and it is very difficult to detect an interaction. Since this material, whatever it may turnout to be, is very difficult to sense with our current technology and the scientific community is not willing to say uneqivocally what this material is.

Mitchell, I'm not "hung up" on the name. I understand that by "dark" the scientific community means non-energetically radiant.

TReed... OK, I'll bite, if this supposed dark matter is made up of neutrinos, and it supposedly makes up 70% of the total mass of the universe then neutrinos should also make up 70% of the mass of everything we detect around us. Now, it may very well be true that billions of neutrinos are passing right through me at this very moment, but they can only do that because they have virtually no mass, if any at all. I don't understand exactly what neutrinos are (does anyone?) but they seem to me to be rather like electrons, but with with no charge, and they travel at the speed of light, so that would also imply that they are virtually massless.

I'm sorry, but I just cannot accept that virtually massless particles make up 70% of the mass of the universe. That makes no logical sense. Could it instead be ionized hydrogen, or basically free floating protons? They at least have mass.

As to a dark matter "halo" around the Milky Way, would this be analogous to the Oort cloud around our solar system? Is the Oort cloud detectable, using infrared telescopes? Do free floating rocks and ice in deep space radiate enough heat to be detectable? or do we just know that's there from observing comets? According to wikipedia:

Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System and many of the centaurs and Jupiter-family comets as well. (My bold emphasis added)

So if we can't even directly observe the solid icy matter that surrounds our own solar system, with visual light or with infrared detection, how do we know that there is not absolutely massive amounts of this type of junk scattered throughout (and as you imply) all around the entire galaxy in a galactic sized halo? In some galaxy pictures, like the famous "Sombrero Galaxy" I'd swear you can almost see it reflecting a diffuse light from the other radiant sources.

One final question... has anyone ever attempted to estimate the mass of the entire Oort cloud? If so, how would that relate to the mass of the sun and the planets? Apparently the answer to this is yes. Again from wikipedia:

The outer Oort cloud is believed to contain several trillion individual objects larger than approximately 1 km (0.62 mi)^[3] (with many billions with absolute magnitudes^[16] brighter than 11—corresponding to approximately 20 km (12 mi) diameter), with neighboring objects typically tens of millions of kilometres apart.^[5][17] Its total mass is not known with certainty, but, assuming that Halley's comet is a suitable prototype for all comets within the outer Oort cloud, the estimated combined mass is 3×10²⁵ kg (7×10²⁵ lb or roughly five times the mass of the Earth).^[3][18] Earlier it was thought to be more massive (up to 380 Earth masses),^[19] but improved knowledge of the size distribution of long-period comets has led to much lower estimates. The mass of the inner Oort Cloud is not currently known.

But what if this is wrong?

To be clear, I should have said "solid chunks of icy matter". I realize that the Oort cloud itself is extremely diffuse. It is also extremely huge in spherical diameter as compared to the solar sytem itself. Sorry about that.

It's more than non-radiant, it means it doesn't block or disperse either (except for it's gravitational pull) which is why hydrogen (ionized or otherwise) isn't your answer.

For clarity's sake, you are solely made up of subatomic particles, along with the Earth, Sun, planets, etc etc, though structured into protons, neutrons, electrons yes.

70% of the mass of the galaxy is not the same as 70% of your mass. Remember, there is a vast void between stars that could be filled with neutrinos. That's a crap load of space. Any given star system only represents a very small (near insignificant) quantity of volume of space a galaxy has. That means that dark matter could only represent .0000000000000001% of your total body's mass, or less.

Think of it this way, take a football field and add say 10 one gallon sized pails full of quarters placed throughout the field. This represents a section of space with 10 star systems. Now let's add dark matter to the field, grid out the field in a 2" X 2" squares and place 1 quarter in them. As you can see, any given pail only gets an added 4-5 quarters, which may only be about 1/500 of the mass in that bucket.

However, given the vastness of the field, if you total up the quarters representing dark matter, it probably could fill up 30 pails or more which is three times the mass of all the star systems out there on the field. This is to get you out the the misconception that 70% of the galaxy mass means 70% of your mass or the planet's mass or star's, it doesn't mean that.

Mitchell

Hmm...very bad first paragraph on my part, so a clarification.

Hydrogen blocks or disperses light, that mean we can account for a certain density or higher in space if either it's being shined upon, or by blocking a light source behind it. Through our observations, this is accounted for, along with He, dust and other such stuff. Yet despite accounting for it, there is still the discrepancy. So it is something that doesn't interact with light except by gravity.

Mitchell

Mitchell,

thanks for the quarters/buckets/stadium analogy. That certainly makes a lot of sense and points out a flaw in my argument. You're right, normal matter and dark matter would not necessarily be evenly distributed. I understand that the notion is that D.M. is supposedly clumped in various regions and has even been "mapped", as I mentioned above.

You mention that ionic hydrogen, He, dust and other such stuff has been observationally accounted for. I'm not calling your statement into doubt, but I never hear this mentioned in articles on this topic. Perhaps the material I'm reading is too generalized or simplified for public consumption. Could you point me to some good resources that deal with how this "accounting" is done. I really am genuinely curious.

Lastly, you stated: "So it is something that doesn't interact with light except by gravity." Do neutrinos do this?

Thnaks for your response. This has been an interesting and illuminating discussion so far. (Pardon the terrible pun).

hehehe, always love a pun; good, bad, or otherwise. :-)

I wish I could point you to some sources, but I don't have any on hand. I just remember from astronomy back in college that we spent a little bit of time going over methods of calculation. And I do remember back a few years ago when it became more mainstream and being vetted by colleagues and amateurs that they asked about H, He, dust and stuff and they've said it's been taken into account as quantifying that has been going on for decades. Perhaps if you ask Michael, he would know a good few places to start on the web. Otherwise if you have access to a good book store that carries books on astronomy you should be able to find a few chapters dealing with it.

As far as everything I've read goes, neutrinos and some other subatomic particles don't interact with light other than by gravity (since it's supposed to have mass). I suppose there's a caveat that if you create a dense enough grouping of them that they could but you wouldn't find that under normal conditions.

I'm glad the quarter analogy helped out :-) And yeah, given that it does have mass, you would expect it to sort of lump together in areas instead of being uniformly distributed. It might be a lot like half mixed gravy. You have some spots here and there that are rather dense, but realistically it's everywhere.

Mitchell

PS: Keep in mind that this hypothesis still might not be correct, our observations and/or equations could be wrong. I'm just trying to help explain where this idea is coming from. :-)

Obviously, I'm no expert astrophysicist or cosmologist, but I am firmly in skeptical agreement with you, Mitchell, that "our observations... could be wrong." The present situation just seems way too cumbersome and full of assumptions and compensations and outright guesses. I prefer to think that at some point some sort of observational/conceptual breakthrough will occur which will bring everything into a new light (there I go again) and we will look back on this current period of confusion in the same way that Copernicus looked at the Ptolemaics and their system of epicycles... "Sure, you can do it that way, but it's ridiculously over-complicated and only approximates the results. See now, if you look at it this way, it's all so elegantly simple." And the Ptolemaics all slapped their foreheads in disbelief at how misguided they had been.

I don't know what that breakthough will be, but when it comes, it should revolutionize everything. I guess I'll leave it at that.

Nice chatting with all of you.

I would say be careful, Occam's Razor just doesn't play nicely in physics.

Everything is made of 4 elements->well there's actually many elements-> well realistically it's a large quantity of different atoms-> except for the fact that atoms are made of protons, neutrons, and electrons->how do you explain antimatter then? Oh, we'll include those too-> you people don't have a clue, you see, there's these subatomic particles which combine to form the previous. The really neat part, is that describing the states these particles are in uses matrices. Matrices? what are you on (and where can I get some)?

Or, look at Newton, then Einstein, what if M-theory is right?

Physics is full of complications, it is very complex. Don't think the easy answer is most likely the right answer, physics is littered with those discarded suppositions. 'Course, sometimes it's nice and neat, E=mc^2.

It's a wonderfully complex universe out there Mikey, don't be too quick to sell it short. :-)

Mitchell

I think that is exactly the plan and is why the artcle says that the picture will take shape as more data is added and that the picture won't be ready for 3 years or so.

No, I meant even larger than Earth's orbit and multiple antennas. Highest possible resolution in our solar system.

No, I meant even larger than Earth's orbit and multiple antennas. Highest possible resolution in our solar system.

Ahh. Well an antenna like that would be great for all kinds of observations!

Butterfly - First thing to realize is that matter is mostly empty space. With enough force, atoms can become smaller to the point that the electrons become part of the nucleus. The blackhole core itself is not a single point, it is a tightly compacted ball of matter. I can tell you that math involved is really nasty, if are ever curious the math used is based in differential geometry.

Imagination has little to do with education or intelligence. All you need is desire, and you sound like you're well qualified already.

@TReed

Actually, current theories (and the math they are based on) do suggest that the central point of the black hole is, in fact, a single infinitely small point (the singularity) where time and space become infinite and therefore physics, as we know it, break down. By definition, the term "singularity" in mathematics means "singular point". There is no tightly compacted ball of matter in these theories.

To my understsanding, the 'singularity' is largely a mathematical construct to describe something that has exceeded the ability for mathematics to fully describe it (everything goes to infinity and we know that infinities do not really exist). Sounds a bit twisted, but standard physics completely breaks down when trying to describe a fully collapsed star that forms a black hole. So they use a single point to describe its characteristics (e.g. gravity, energy, etc.). What is really at the center of a black hole, we don't know (althought quantum physics seems to be able to partially describe it).

Certainly, no one knows what truly lies at the center of a black hole (or how many licks it takes to get to the center of a Tootsie Roll Tootsie Pop), but physicist do believe that the singularity is an infinitely small and infinitely dense point, not a ball of matter with a measurable size.

This is (very interestingly) the same kind of math that describes the universe just at the moment of the Big Bang. The preailing wisdom is not that there was a bowling ball sized chunk of matter that expanded during inflation to create the universe, as we know it. The thinking is (and the math dictates) that there was an infiniately small and dense point that inflated.

To me, this symmetry between black holes and the moment of the big bang, is more than a coincedence. I believe that a black hole is what spawns a big bang and that as long as the black hole is actively feeding that the universe it spawned continue to expand as more matter and energy are pushed into that universe from the black hole on the other side. When the black hole evaporates, the universe it spawned is left behind to evolve.

@ Scott

While I don't claim to be an expert on the matter, I have seen experts postulate it either way. Basically, the matter within the black hole could be in a singularity, or could occupy a space up to the size of the event horizon. In the event of the matter not being within a singularity, they say that the math is no longer describing the volume of space occupied, but the nature of the matter.

Since all of it is highly speculative, and we have nothing more than mathematical models and gravitational effects to go off of, it's hard to say with any authority exactly how much space this stuff occupies. We can infer it's mass due to the gravitational effects, but the volume is more of a mystery due to our inability to truly test it. I just think some of the astrophysicist are being more honest when they say what they know, and what they think.

"The blackhole core itself is not a single point, it is a tightly compacted ball of matter."

Uh, actually, half-wit, it is a single, infinitely small point. That tells me all I need to know about what you can "tell me," which is nothing.

A math lesson is needed here. A singularity in mathematics is a portion of a function that is undefined. Based on Einstein's theory of relativity, the mathematics goes to a singularity because the equation eventually is divided by zero, thereby creating an undefined result.

The compaction of the matter in a blackhole is due to the curvature of the space. One definition of the matter within a blackhole is called quantum foam. Another thought involves spinning blackholes in which the matter creates a spinning torus. Here is a link to a paper explaining why the matter can not collapse to a singularity: http://www.cr-theory.org/pdf/Time-Frozen-5.pdf. Think also of string theory, where six dimensions are compacted to Calibi-Yau manifold. If the space is so curved that all dimensions become compacted, the center of the blackhole could become a zero-dimension space.

MarkC - Obvious from your comment your lack of knowledge of physics is evident. Any infinity is bad, it means that the math falls apart. When the math fails, the physics cannot prove what is happening. And since you have to come up with name calling with an ad hominem argument in place of a scientific argument shows your own ignorance.

@Mitty

With all due respect, you are incorrect. The meaning of "singularity" is not in dispute, nor is it interpreted differently by physicists. While it is true that there is no actual proof of what's inside a black hole, the math is quite clear that the gravity well is so pronounced at the core of the black hole that its effects would result in all matter condensing down to a single point of infinite mass and density.

There really isn't any debate on this interpretation in the actual scientific community, as you claim that there is.

@TReed

Your claim that an infinite result is essentially meaningless is not actually factual. There is a lot that can be inferred from infinite results. We know that the speed of light is a constant velocity that can't be broken because Einstein's equations say that you'd need infinite energy to accelerate to that point and if you did, you'd have infinite mass.

The equations that model what happens to matter inside a black hole tell us that the matter reaches a single point of infinite density and infinite mass (thus, the term singularity, not the term "measurable ball of matter").

As for your bringing quantum foam, string theory and multi-dimensions into the discussion, none of those things have any scientific relationship to the physics of black hole singularities.

And, your link is not evidence of anything as it simply a web site run by a person making broad assumptions by linking loosely coupled concepts to come up with results that have no actual scientific support.

Scott - The problem with a single point of infinite density and infinite mass is an attempt to explain the undefinable. This is where the problem of merging relativity with quantum mechanics occurs. As the space gets compacted it will reach levels where quantum mechanics takes over and that transition is not solved. So when I say "a compact ball of matter", I am thinking in terms of quantum mechanics. My inital statement was poorly explained, but it was an attempt to not overwhelm the person that I was responding to with too much information and as a result I provided not enough information.

Quantum foam was a description of not only matter, but space and time near the "singularity" and was presented as an alternative view of the core of a blackhole. String theory and zero dimensionality is an attempt to explain the extreme curvature of the spacetime within a blackhole of which a Calibi-Yau manifold is the best mathematical description that I know of. If you know of a better compaction model, I would be interested to hear about it. I have a personal interest in n-dimensional spaces, topological spaces and differential geometry.

@TReed

The idea of a singularity poses probably one of the greatest mysteries in modern physics for the very reason you state (Gravity is at work in the world of the very large and Quantum Mechanics is in charge in the world of the very small and where does one set of laws stop and the next start?).

But, where you are going wrong is to dismiss that there is or even could be a singularity because of our current lack of understanding of the afore mentioned problem.

Just because science doesn't have an answer to the gravity/quantum mechanics conundrum yet doesn't mean that we have to dismiss what very sound theory and math tell us.

After all, Newton came up with some pretty good laws of motion and how gravity affects bodies without ever really understanding what gravity actually was.

Lastly, I'll just point out again that this debate we're having about if the singularity is a point or a measurable "ball" is, in reality not a dispute at all. There is no debate in the scientific community on this topic. Yes, there are the unanswered questions about exactly what laws take over at what point, but the only debate about what a "singularity" means is in forums like this, where folks take unwarrented "leaps" of logic that are not based in science-fact.

Scott - In the end I can see where my use of the term "ball' can cause so much grief. I think in the terms of mathematics and the language I sometimes use can be mistaken. Especially when I try to explain in very simple terms.

Yes, there more unknowns then knowns when discussing blackholes. And the aspects of the singularity itself is basically unknown, which is due to a lack of means to model that structure. From a quantum perspective, there is a possibility that the curvature could be severe enough to bring the center of the structure down to a one-dimensional string, which would recombine the four forces into one and matter and energy into something we have never seen. This is speculation based on my understanding of quantum mechanics and string theory, and I open this up for discussion with you becuase you seem to have a deeper understanding of this subject then most here.

@Scott

I really don't disagree with anything you've said there. There's no mistaking what a singularity is defined as, and yes, the consensus view is that at the center of every black hole, is a singularity. What I'm saying is: There are people with as many degrees and as much brain power who say that may not be true and here is why"..." Try and remember that Einstein too was once in the minority with his theory of relativity. It wasn't until many of the aspects of his theory were proven true that others jumped on the band wagon.

My point is, don't try and tell everyone how it is, just because we agree that's what it's like. When we have data to back that up, that's one thing, but let's not dismiss the possiblity that we could be wrong.

I do have one question, I'm not clear on though. Do the equations involved take into account the warping of space time due to the extreme velocity of matter falling into the black hole, and warping of space time due to the extreme gravity?

Mitty - The curving of space is due to the matter and should follow that the more matter, the more curvature thought process. Einstein used something called a Ricci curvature tensor, which is a generalized equation describing curved space.

@Mitty

I don't think I dismissed anyone views of what could "possibly" be happening. I responded to and continued to rebuke a statement that there is some sort of real debate as to what the math and theories say about what lies at the center of a black hole.

It "could" be that unicorns and leprichons are there, but there is no scientific basis for that. What there is a scientific basis for is the inner workings of a black hole right up to the point of the singularity.

I think that sometimes people tend to get too caught up in the incorrect assumption that we can't know "anything" about what goes on in a black hole. That is not actually true. A black hole is a star that has collapsed under its own weight. General Relativty and Newtown's Laws can describe what lies beyond the event horizon quite well and this should not be surprising. It's what happens at the core where most of the real scientific mystery is.

I personally believe that all that matter pulling down on itself "rips" the fabric of space/time and manifests itself in a Big Bang that begins a new universe. But, that is my "belief" of which I have no scientific evidence and you will never hear me present this view as fact.

Spending in the sciences is tiny when compared to the US budget, it wouldn't put a dent in the deficit.

As TReed said; the spending on science - and in particular on astronomy is minuscule in our economy. The US spent over $41B on our pets last year and $70B on lottery tickets (largely for the right to recycle a brightly colored piece of paper).

Let's not forget that this particular effort is something that only a few years ago was estimated to be "impossible in our lifetimes" but now we stand on the brink of solving the mathematic, computational, and engineering challenges to accomplish it. That will spill over into unrelated industries, train our new technical students, and open research areas we had not thought of. I'll try to draw a similar parallel the next time I'm cleaning the neighbor's dog feces off my shoe.

@node4

While I agree with your and TReed's sentiment, your figures on what we spend money on is not a correct rebuttal. The comment was about the US budget, not what Americans "choose" to spend their money on.

I sort of see your point ScottM, but on the other hand, we do have elections where we select our representatives and they ultimately choose how to allocate our funds. If enough of us are unhappy with those choices, we can have them change that. It's certainly not the instantaneous gratification that we have when we walk into a gas station and purchase a lottery ticket (controlled by that same election process coincidently), but it's a series of choices none the less.

This is why some people choose to contribute privately to scientific endeavors so their wishes are not diluted by the rocket scientists in Clowngress.

@node4

The amount spent on lottery tickets and our pets is not decided by politicians, the US budget is.

I don't think we are in disagreement about who determines the US budget, but we have a representative government and we elect those representatives (politicians) - so ultimately, we are responsible. Please note that those same representatives determine the payout on the tickets, where they are sold, and how often.

@node4

And what do those representatives you talk about have to do with what Americans spend on their pets or lottery tickets?

Your original point reads (whether you intended it to or not) as if you believe that the US Government has control of the amounts of money spent on pets and lottery tickets and it implies that this spending is wasteful, when compared to what we could be gaining if we put that money towards scientific research.

My replies have been simply trying to get you to understand that the US Government has no control over the money that is spent on pets and lottery tickets, and so your point makes no sense.

@ScottM - *sigh* ... actually you mist the point completely that I am trying to make; that people spend a great deal more money on items like their pets and lottery tickets (which I personally consider trivial), yet complain loudly about smaller amounts spent on science that benefits society. I never stated that government controls the amount spend on pets or lottery tickets; but rather that we, using our representative form of government control how much we spend on science.

@node4

[sigh] Actually, I did get your point. It's just that your point makes no sense.

If a person complains about the amount spent on science, he or she can't be then blames for the billions of dollars he or she spent on pets or lottery tickets.

Your entire premise is irrational as you are comparing two mutually exclusive things: individual amounts people choose to spend vs. aggregate tax dollars paid begrudgingly.

By the way, I personally disagreed with the US budgets proposed in every one of GWB's year's in office, yet our representational form of government didn't seem to help me change them.

well, lets agree to disagree about your ability to understand anything I said.

Yes, let's also agree to disagree about your ability to make a relavant and meaningful point.

Yes, and lets agree that an ego is a terrible thing to waste on someone on makes irrelevant arguments regarding science and technology.

LOL, I'm the one that pointed out how YOUR analogy (not related to the story by the way) was nonsensical.

But, yeah, YOU'RE the one making relavant on-topic posts.

Ok.

whatever gets you through the night ....

And then we would be another black hole for some other something to discover :)

Event horizon is spherical

The event horizon is spherical, but a rotating black hole is going to pull all matter approaching it into the plane that perpendicularly intersects the axis of the black hole. This is because of the "frame dragging" gravitational effect on space-time that Einstein predicted and has subsequently been proven experientally.

I think you are watching too many Lawrence Krauss comedy shows. :-)

The black hole will act as a lens for light on the far side of it. But, since there is so much dust surrounding the entire region, that "lensed" light can't be seen anyway.

There is no shadow, as it does not emit any light and any light that gets too close is pulled in. I don't think anyone suggested anyting about a shadow.

"I don't think anyone suggested anyting about a shadow."

Other than the article. Which you apparently have not read. Repeatedly.

@Mark

Yes, I did read the article and yes I did miss the word "shadow" as it was followed by "or silloette", which I believe is a better term and the one that I remembered the article saying.

At any rate, it doesn't change the content of my earlier reply.

Well, it's someting like 29,000 light years away and our fastest rockets send a sattelite at about 30,000 MPH. So we could send a probe, but we'd have to wait 648.7 million years for the probe to get there and then another 29,000 years for the probe's signal to get back to us. Oh, and we'd never be able to see what's in the black hole because the probe would be destroyed by spagahettifiation upon entering the black hole and even if it didn't, it wouldn't be able to get a signal back out of the event horizon.

...Or, we could wait the 3 years for the current experiment to show us what it looks like from outside of the event horizon.

but we'd have to wait 648.7 million years for the probe to get there and then another 29,000 years for the probe's signal to get back to us

and chances are that (if we are around for the duration) we would have developed significant technological advancements, over the 648.7 million years, that we would probably end up sending another probe and beating the first one we sent.

Oh give it a break Ad'M, instead of working on your troll credentials.

@Tired

You're funny. Virtually everything you've presented as a fact is completely incorrect and has, up to 500 years of scientific theory, mathematic proof as well as experiemental and observational evidence behind it.

Seriously, if you are indeed interested in understanding more about the nature of our universe, you'd do better to stop being flame bait by glossing over tiny details, like math and experiment that clearly disprove your whacked out ideas.

The bible also doesn't talk about lasers or Teflon or Big Macs.

Just a troll. Move along nothing to see here.

Actually it does Frank...it's hidden in there and you have to look closely to find it. Happy searching!

Unlikely at your Burger King job, I know.